We propose to extend our original observation of a hitherto unknown material isolated from the bovine pineal gland, which will inhibit ovulation. This was found to be effective in blocking the effects of either exogenous gonadotropin or endogenous secretion of gonadotropin. To this end we shall prepare larger quantities and submit the extracts to further purification after which the nature of the active compound will be elucidated by modern analytical methods including mass spectrometry and amino acid analysis. We propose to investigate further the biological activity of the compound using the following experiments: 1. Investigation of the dose/response relationship for inhibition of ovulation by blocking the effect of exogenous gonadotropin with pineal extract and its active constituent isolated in homogenous form. 2. Evaluation of the suppression of endogenous secreted gonadotropin by following inhibition of ovulation indirectly through observing blocking in fertility after copulation.